In Load Resistance Factor Design $($LRFD$),$ the primary safety factor is achieved by$...$

$($a$)$ factoring $($multiplying by more than $1\mathrm{.}0)$ the live and dead loads.$$

$($b$)$ calculating a resistance factor for material irregularities in the structural members.

$($c$)$ reducing the allowable strength used of the structural members.

$($d$)$ allowing full strength capacity of the structural members.